In my opinion Apple's Time Capsule (TC) is a fantastic little product. Since obtaining one in late 2009 I have not had to worry about the hassle of backing up both computers in our house as they are made wirelessly using Apple's built in Time Machine software. I could harp on about how much I like the Time Machine / Capsule combo but that's not the point of this post.
At the time of purchasing I was unaware of the major flaw in the TC's design: it's cooling system is rubbish and as a result, the device runs hot, shortening the life of the power supply. In my crude temperature measurements, during a 4 GB backup, I measured the surface temperature of the white plastic cover - directly over the power supply to be 109F / 43C. I think I have felt it even hotter in the past but with no measurements I can't back this up. There is a fix however, to modify the case so that adequate ventilation can cool down the heat generating power supply.
Credit
Credit for the modifications you see here belongs to LaPastenague*(Ray Haverfield) and Chris Fackrell**. Please visit their links for the original information I based my repair on. Both of these gentlemen offer a Time Capsule repair service if you live in Australia (Ray - LaPastenague) or the UK (Chris). Another excellent resource for information is the Apple Support Discussions.
Disclaimer
I should make a short disclaimer that neither aforementioned or I are responsible for any damages you cause to your own TC or yourself should you choose to repair or modify it yourself. I imagine the moment you open the enclosure, if not when you drill the holes you will void any warranty you have remaining on your TC. Also, if you are not familiar with working with electrical devices and components you should either take the time to learn about them, get a professionals help or don't proceed any further. There is the possibility to seriously hurt or kill yourself with electricity.
So Here GoesFirst things first I unplugged the TC and carefully placed it upside down on a towel to protect the original finish.
Figure 1. Under side of the Apple Time Capsule.
Figure 2. Fan that is included in the Time Capsule. It's aimed directly at the hard drive, 90 degrees away from where it's needed most...
my trusty sharpie and marked the locations for the holes for the screws that fasten the back plate. There are ten screws...
Figure 3. Using a Sharpie to mark out the holes to punch.To make the cleanest holes I chose to use a hole punch based on Chris Fackrell's recommendations. It just so happened that scrapbookers often use a tool like the one below and since my wife is a scrapbooker she happened to have one in her toolkit. She got it from the local craft store for less than $5, including two tips, one being ~5 mm diameter. Remove the silicon mat from the aluminum back-plate again and place it on a sacrificial surface like a piece of scrap wood. Take your time to line up everything so you do a good job.
Figure 4. Hole punch with exchangeable tips.
Figure 5. Approach for removing the fan from the back-plate.Once the fan was off I used my trusty sharpie to mark out where I wanted the hole for the fan inlet. I drew lines as shown in the figure below so that the new hole would line up nicely with the inlet of the fan.
Figure 6. Use a punch to make a dent in the base-plate (I used an old screw) to make a clean pilot hole.Once marked out, I clamped the base-plate and the silicon boot to some wood and drilled away. I used a 40 mm hole saw.
Figure 7. Clamping assembly for hole drilling. What a great excuse for using power tools...Recommendation: If I could do this again, I would have done the following: used some scrap paper and tape and to protect the small holes during drilling. I didn't do it and subsequently spent 30 minutes with a pair of tweezers picking off metal shards from the sticky silicon boot.
Figure 8. Dozens of little metal shards that need to be removed because I didn't cover up the little holes in the base-plate. After drilling I used a file and some sand paper to finish off the hole. I also took the precaution to wash the base-plate to remove any unseen shards.
Figure 9. All done! Next step is to do the electrics...
Electrics
The next step in the whole process is to modify the wiring for the TC fan so that the fan is always on. The explicit instructions for this process can be found at LaPastenague's site. I chose to enlist the help of a friend to do the soldering. Rob did a stellar job for me, much appreciated!
Figure 10. Rob working on putting the resistors in the 5V fan line.Rob had two 1/2 watt 100 ohm resistors (50 ohm actual) that he wired in parallel and soldered to the 5V line.
Figure 11. Two 100 ohm resistors wired in parallel.We cut the two center wires to the fan plug and wired in the resistors. Once wired in, Rob did a nice job of heat shrinking over the resistors. We ended up adding about 20 mm extra length to the 5V side just to allow a more easy fit when reassembling.
Figure 12. Half of the fan modification is now complete. Next is to seal up one side...Next up was to put something in place to protect the fan from little fingers. I cut out the protective grill shown below from an old power supply. Some mod's I have seen mount mesh or grills on the inside of the enclosure, I chose to mount it on the outside so that should something happen, the grill can't dislodge and move around in the enclosure. To direct the fans output to the power supply, you will need to tape over the outlet as shown below. I used packing tape taped to itself to make my cover.
Figure 13. Template for sealing one side of the fan. 
Figure 14. Fan mod. The white patches were the well intended insulation. A bit more electrical tape and the job was done. I added in some small foam pockets to my job. Perhaps for my own peace of mind, my thinking was it would isolate the fan from the circuit board below. Then I realized there was one more step to go.
As Chris Fackrell shows on his page, you need to shorten the rubber grommets that were originally holding the fan to the base-plate. This is easier than I thought, it's removing them that's a pain. I used a little Vaseline, a 1.5 mm Allen key and a lot of patience. Gently work the the small end of the grommet out. Be patient and you'll eventually get it.
To do the shortening mod, you'll need scissors and Crazy Glue (or any cyanoacetate super glue). I cut 5 mm out of the grommets and glued the two halves back together with Crazy Glue. This mod will keep the fan close to the base-plate and away from the circuit boards.
Figure 15. Shortened rubber grommets.Insert the grommets back in the fan first, then use a small Allen key to push the fat end of the grommet through the base plate. The fan can be reconnected to the connector on the board and you should see the fan start up when you plug in the mains power.
Just for fun I thought I would see how much air is being blown. Using my Anemometer (for kiting) I measured a steady flowrate of 2 m/s. I also measured the external temperatures of the unit after it had been running for a while. I used a personal thermometer. This is probably not the greatest device to use for the mod but it gave me a relative change showing that the fan mod worked.
Figure 16. Anemometer measuring a flowrate of 2.0 m/s out of the modified fan.If I put my hands near the upper vents on the outside of the TC I can feel a small amount of air movement. A good sign that heat's being removed by convection!
Figure 17. Exterior surface temperature of my modded Time Capsule.Before the modification I saw temperatures of 109 F/ 43 C, possibly higher. A few days after the mod, the temperature seems to be stable between 94-98F / 34-36 C. Overall, I am really happy with the final result. I have the capacitors tucked away in case the power supply does crap out yet. I'll update here if I make any further changes.
Update** - I forgot to post these pics. Below you can see the holes punched for the TC base plate as well as the fan opening.
Figure 18. Time Capsule base plate and fan-mod opening.I eventually used some stick-on feet from a local hardware store.
Figure 19. The final product working happily away. Once again, I would like to say thanks to Ray Haverfield (LaPastenague) and Chris Fackrell for offering up their time and information to make it possible for people like me to do this themselves.
